evolution n.
Skip this Video
Loading SlideShow in 5 Seconds..
Evolution PowerPoint Presentation


457 Views Download Presentation
Download Presentation


- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Evolution • Chapter 15

  2. Darwin’s Theory of Natural Selection

  3. Evolution •

  4. Evolution • Is it correct to say that Evolution is just a theory? Is gravity just a theory? Defend your answer.

  5. Biological Evolution • All the changes that have transformed life on Earth from the earliest beginnings to the diversity of organisms in the world today. • Unifying theme of biology.

  6. Biological Evolution • Microevolution: evolution on a small scale, affecting a single population. • Macroevolution: evolution on a large scale affecting changes in species across populations.

  7. Charles Darwin • 1809-1882 • Darwin boarded the HMS Beagle in 1831. • Darwin’s role on the ship was as a naturalist and companion to the captain. • Darwin collected biological and geological specimens during the ship’s travels.

  8. Charles Darwin

  9. Charles Darwin • Over the 5 year-voyage, Darwin collected rocks, fossils, plants, and animals. • Darwin also read Charles Lyell’s Principles of Geology which influenced his thinking about the age of the Earth.

  10. Charles Darwin • In 1835, the Beagle arrived in the Galapagos Islands. • This is where Darwin collected many new specimens and began to observe the differences in the varieties of animals among the different islands. • Darwin was intrigued with species diversity and conceived his theory of natural selection in 1838.

  11. Galapagos

  12. Natural Selection • Darwin’s theory had 4 basic principles that explained how traits of a population can change over time. • 1) Individuals in a population show differences or variations • 2) Variations are inherited • 3) Organisms have more offspring than can survive on available resources. • 4) Variations that increase reproductive success will have a greater chance of being passed on.

  13. Natural Selection • Results in changes in the inherited traits of a population over time. • These changes increase a species’ fitness in the environment. • 4 Main Principles • 1) Overproduction of offspring • 2) Variation • 3) Adaptation • 4) Descent with Modification

  14. Natural Selection • Variation exists within the inherited traits of the individuals. • An organisms phenotype may influence its ability to find, obtain, and utilize its resources and might affect the organisms ability to reproduce. • Phenotypic variation is controlled by the organisms genotype and environment.

  15. Variation

  16. Variation

  17. Natural Selection • Adaptation leads to the increase in frequency of a particular structure, physiological process, or behavior in a population or organisms that makes the organism better able to survive and reproduce. • Fitness: used to measure how a particular trait contributes to reproductive success.

  18. Adaptation

  19. Natural Selection • Overproduction of offspring: The ability of a population to have many offspring raises the chance that some will survive but also increases the competition for resources.

  20. Overproduction • Average cardinal lays 9 eggs each summer, if each baby cardinal survived and reproduced, it would take only seven years for the first pair to have produced one million birds.

  21. Natural Selection • Descent with modification: as the environment of a population changes, the entire process of natural selection can yield populations with new phenotypes adapted to new conditions. • Each successive living species will have descended, with adaptations or other modifications, from previous generations.

  22. Descent with Modification

  23. Descent with Modification

  24. Natural Selection •

  25. Natural Selection • What are the 4 components of Natural Selection? How does Natural Selection affect Hummingbird populations?

  26. Shaping Evolutionary Theory

  27. Why Does Evolution Matter? • • Why is the theory of evolution important to doctors and the field of medicine? How does it affect the way illnesses and treatments are approached?

  28. Continuity of Life • Recall: • All life that has existed on Earth share at least the same 2 structures, Nucleic Acids (DNA and RNA) and Protein.

  29. Continuity of Life • Recall: • All ecologically successful organisms have reliable means of passing genetic information to offspring through reproduction. • Sexual Reproduction: 2 parents, meiosis, gametes. • Asexual Reproduction: 1 parent, genetically identical offspring.

  30. Continuity of Life

  31. Continuity of Life • The genetic view of evolution includes the transfer of genetic material through reproduction. • The continuity of a population/species depends on the process of reproduction.

  32. Mechanisms of Evolution • Population Genetics • Natural Selection • Molecular Biology

  33. Population Genetics • Genetic Drift is the random change in the frequency of alleles of a population over time. • In large populations enough alleles “drift” to ensure the allelic frequency of the entire population remains constant from generation to generation. • In smaller populations the effects of genetic drift become more pronounced and the chance of losing an allele becomes greater.

  34. Population Genetics

  35. Population Genetics • Founder Effect • Extreme example of genetic drift. • Occurs when a small sample of a population settles in a location separated from the rest of the population. • Alleles that were uncommon in the original population might become common in the new population.

  36. Population Genetics • Founder Effect • Amish Communities • 6-Finger Dwarfism

  37. Population Genetics • Bottleneck • Occurs when a population declines to a very low number and then rebounds. • The gene pool of the rebound population is often genetically similar to that of the population at its lowest level, reduced diversity.

  38. Population Genetics • Bottleneck • Cheetahs • European Bison

  39. Population Genetics • Gene Flow • The movement of genes into or out of a population. • Occurs during the movement of individuals between populations which increases genetic variability.

  40. Gene Flow • Migration

  41. Population Genetics • Nonrandom Mating • Limits the frequency of the expression of certain alleles while increasing the frequency of expression of other alleles. • Organisms usually mate with individuals in close proximity which promotes inbreeding and leads to changes in allelic proportions that favor homozygous individuals.

  42. Nonrandom Mating • Mating preferences

  43. Population Genetics • Mutations • Increase the frequency and types of allele changes within populations (genetic variability). • Provide raw material for which natural selection works.

  44. Population Genetics • Mutation • Resistant Lice

  45. Population Genetics • Hardy-Weinberg Principle • When there is no change in the allele frequencies within a species, a population is said to be in genetic equilibrium. • p + q = 1

  46. Population Genetics • Hardy-Weinberg Principle: there are 5 conditions required to maintain genetic equilibrium • 1) Population must be large with no genetic drift occurring • 2) No movement in or out of a population • 3) Must be random mating • 4) No mutations within the gene pool • 5) Must be no natural selection.


  48. Natural Selection • Acts to select individuals that are best adapted for survival and reproduction. • Three main ways natural selection alters phenotypes: • 1) Stabilizing selection • 2) Directional selection • 3) Stabilizing selection

  49. Stabilizing Selection • Eliminates extreme expressions of a trait when the average leads to higher fitness.

  50. Directional Selection • Occurs when an extreme version of a trait makes an organism more fit.